The invention relates to a device for the retention of core melt-through-in the event of a core melt-through accident in light-water reactors and also to a reactor plant having such a device. Because of the afterheat of the reactor core, which is produced because of the radioactive fission products, the core melts if the cooling water empties from the reactor pressure vessel because of an accident; the molten mass of the core penetrates the wall of the pressure vessel. If there is no retention device to collect the molten mass, then the foundation of the building is also breached by the molten mass, with the concrete being decomposed because of the high melting temperature (over 2500.degree. C.) with the formation of hydrogen, carbon monoxide, carbon dioxide and water vapour. The molten mass of the core is essentially composed of uranium oxide, zirconium and steel in the ratio of roughly 6:1:3.
Various safety concepts have been developed to prevent the hypothetical consequences of serious accidents in light-water reactors, in particular of core melt-through accidents. Thus for example a core melt-through retention device ("core catcher") has been proposed, in which a shaft-like collecting basin for the molten mass is provided beneath the reactor core (R. Hammond, J. Dooley, 1982 "Retrofitting Core Catcher to Nuclear Plants", NUREG/CR-2941; or U.S. Pat. No. 4,036,688). This known device consists of an upper section, which is cylindrical (diameter: 3.5-5 mm, height: 10-15 m) and a lower section, which tapers conically downwards (height: 20-25 m). The upper section is lined with highly refractory material and the lower section is constructed as a water-cooled, double-walled steel crucible. This crucible is filled with a siliceous or oxidic ceramic bulk material. With the cooling system provided there is the danger of the inner crucible wall being perforated by the molten mass, as a result of which radioactive fission products of the molten mass can be released into the atmosphere.